I want to know what is the function of the little tube who's connected under the carb and go nowhere under the quad. Is it a vent or an overflow because I recently cleaned my carburetor and now when I turn ON the valve on the gas tank, the gas is leaking from that tube.
Can anyone help me out please?

 

You're talking about the one right off the bottom of the carb right?

that has a little setscrew where it connects to the carb. It's your float bowl drain line and if your floats stick, or if you have a dirty needle valve you will get gas flowing out of that line whenever your tank is in the "on" position.

First thing I would check is to see if that little set screw is tight. If it's tight and you still have the flow through problem .. take the carb off and clean it out really well. Make sure your floats are set correctly as well.

Good luck!

 

yep you got **** in your carb...happend to my warrior almost every week it made me so mad to have to clean it every time, it was stuff in the needle and seat.

 

I already cleaned my carb but I guess I'll remove it again to check the needle, and also by the way how do I adjust the float setting?

 

and that is a overflow

 

That little line provides 3 functions. Its a vent for the float bowl, its an overflow for when there is a problem and its a drain.
The screw will open the passage for the drain, but has no effect on the vent or overflow...they cant be shut. If you look at my picture page, there is a picture of the inside of the float bowl, and you can see the brass tube that sticks up...its the vent/overflow tube. The drain is at the bottom of the bowl.
If gas flows out the overflow, then the float is hung up...most likely the needle and seat are being held open by crud.
As long as youre gonna be working on it, put an inline fuel filter in the gas line, and thatll help keep the crud out of the float bowl.
Welcome to the forums.